In conventional processes, the method of making contacts and interconnecting lines in integrated circuits typically includes at least the following two mainly sequential steps: (1) the formation of the contact holes, and (2) the formation of the interconnecting line patterning. More specifically, a typical conventional procedure includes five main process steps: (1) contact holes photolithography, (2) contact holes etch, (3) film deposition, (4) interconnecting lines photolithography, and (5) interconnecting lines etch. FIGS. 1-5 illustrate a conventional method of making contacts and interconnecting lines.
FIG. 1 shows the cross-section of an intermediate structure in forming a contact and interconnect line. Using conventional processes, a patterned photoresist layer 14 is formed on a dielectric layer 10 that covers a conductive area 12. Typically, dielectric layer 10 is an oxide layer or a borophosphosilicate glass (BPSG) layer. The conductive area 12 is formed on the bottom of the dielectric layer 10. The conductive area 12 is either a source/drain region or polysilicon gate electrode. The photoresist layer 14 is patterned for making a contact hole in the dielectric layer 10 to the conductive area 12.
FIG. 2 shows the cross-section of the structure after a contact hole 13 is formed by etching. More specifically, the portions of the dielectric layer 10 left uncovered by the photoresist layer 14 is anisotropically etched and the photoresist layer 14 is removed. Thus, a contact hole 13 is formed, thereby exposing the conductive area 12.
FIG. 3 shows the cross-section of the structure after depositing a conductive layer 16 on the dielectric layer 10 and conductive area 12. Typically, a metal, such as aluminum, is deposited by chemical vapor deposition (CVD) in this step. In general, it is preferrable that when depositing the conductive layer 16, the conductive material entirely fill the contact hole 13. Depending on the aspect ratio of the contact hole 13, the step coverage may be relatively poor.
FIG. 4 shows the cross-section of the structure after a second photoresist layer 18 is patterned on the conductive layer 16. The photoresist region 18A forms a mask for making an interconnect line, and the photoresist region 18B forms a mask for making a contact.
FIG. 5 shows the cross-section of the structure after an interconnect line 21 and a contact 20 are formed. To form the interconnecting line 21 and the contact 20, an anisotropic etch is performed to etch the conductive layer 16 left uncovered by photoresist regions 18A and 18B. Then the photoresist regions 18A and 18B are removed in a conventional manner.
There are three main problems with these conventional processes. First, the interconnecting lines patterning is susceptible to under-cut and sidewall corrosion during the etching process. Second, the formation of the contact is susceptible to nonconformal step coverage at the opening of the contact hole. The third problem is the interface problem between the contact plugs and interconnecting Hues. The applicants are not aware of any conventional methods to solve the second and third problems. Typically, manufacturers try to control the reaction conditions in order to minimize the interface and nonconformal step coverage problem. In response to the first problem, traditionally, cleaning steps are required after etching, but these cleaning steps make the fabrication process more complex and generates the other problems.